add new explicit method for enabling backlight depending on output type

ensure that nested compositors don't mess with backlight

src/bin/e_backlight.c

@@ -121,9 +121,7 @@ e_backlight_level_set(E_Zone *zone, double val, double tim)
    // set backlight associated with zone to val over period of tim
    // if tim == 0.0 - then do it instantnly, if time == -1 use some default
    // transition time
-   if (eina_streq(ecore_evas_engine_name_get(e_comp->ee), "buffer") ||
-       strstr(ecore_evas_engine_name_get(e_comp->ee), "wayland"))
-     return;
+   if ((!e_comp->screen) || (!e_comp->screen->backlight_enabled)) return;
    if (val < 0.0) val = 0.0;
    else if (val > 1.0)
      val = 1.0;

src/bin/e_comp.h

@@ -76,6 +76,7 @@ typedef struct E_Comp_Screen_Iface
    /* is key event eaten */
    Eina_Bool (*key_up)(Ecore_Event_Key *ev);
    Eina_Bool relative_motion : 1;
+   Eina_Bool backlight_enabled : 1;
 } E_Comp_Screen_Iface;
 
 /* struct to hold canvas objects so that abi doesn't break

src/bin/e_comp_x_randr.c

@@ -23,6 +23,7 @@ E_Comp_Screen_Iface xiface =
    .create = e_comp_x_randr_create,
    .apply = e_comp_x_randr_config_apply,
    .relative_motion = EINA_FALSE,
+   .backlight_enabled = EINA_TRUE,
 };
 
 static void

src/modules/wl_drm/e_mod_main.c

@@ -821,6 +821,7 @@ static E_Comp_Screen_Iface drmiface =
    .key_down = _drm2_key_down,
    .key_up = _drm2_key_up,
    .relative_motion = EINA_TRUE,
+   .backlight_enabled = EINA_TRUE,
 };
 
 static Eina_Bool